In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way outflow valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. The valves separate the chambers of the heart, and are each mounted in an annulus therebetween. The annuluses comprise dense fibrous rings attached either directly or indirectly to the atrial and ventricular muscle fibers. The leaflets are flexible collagenous structures that are attached to and extend inward from the annuluses to meet at coapting edges. The aortic, tricuspid, and pulmonary valves usually have three leaflets, while the mitral valve usually has two leaflets.
The operation of the heart, and thus the patient's health, may be seriously impaired if any of the heart valves is not functioning properly. Various problems can develop with heart valves for a number of clinical reasons. Stenosis in heart valves is a condition in which the valves do not open properly. Insufficiency is a condition which a valve does not close properly. Repair or replacement of the aortic or mitral valves are most common because they reside in the left side of the heart where pressures and stresses are the greatest. In a valve replacement operation, a replacement prosthetic valve is implanted into the native valve annulus, which may involve excision of the native valve leaflets.
Heart valves may lose their ability to close properly due to dilation of an annulus around the valve or a flaccid, prolapsed leaflet. The leaflets may also have shrunk due to disease, such as rheumatic disease, thereby leaving a gap in the valve between the leaflets. The inability of the heart valve to close will cause blood to leak backwards (opposite to the normal flow of blood), commonly referred to as regurgitation. Common examples of such regurgitation include mitral valve regurgitation (i.e., leakage of blood through the mitral valve and back into the left atrium) and aortic valve regurgitation (i.e., leakage through the aortic valve back into the left ventricle). Regurgitation may seriously impair the function of the heart because more blood will have to be pumped through the regurgitating valve to maintain adequate circulation. In early stages, heart valve regurgitation leaves a person fatigued and short of breath. If left unchecked, the problem can lead to congestive heart failure, arrhythmias, or death.
Heart valve regurgitation may be caused by changes in the shape of the heart valve annulus, damage to one or more heart leaflets, and/or damage to the chordae tendinae. In such regurgitation, the heart valve leaflets no longer coapt together properly to seal the valve, so that instead of the leaflets coapting to fully close the valve annulus during systole, an opening remains between the edges of the leaflets.
Dysfunctional heart valves, such as those where the leaflets no longer coapt for proper sealing during systole, can be repaired or replaced with prosthetic devices such as prosthetic valves. In some cases, it may be desirable to remove native structures such as valve leaflets in order for the prosthetic valve to be properly implanted within the native valve annulus. For example, in traditional open heart surgical procedures, a surgeon uses a scalpel to manually cut native heart valve leaflets. In some cases, a replacement valve can be installed directly over a native valve, without the need to remove or cut native structures such as valve leaflets. For example, in transcatheter aortic valve replacement (TAVR) procedures, the prosthetic valve is delivered through a catheter and deployed within the native valve annulus by pushing native leaflets to the side. In some cases, it may be desirable to cut (e.g., bisect) native leaflets in order for the prosthetic valve to be properly deployed within the native valve annulus. Examples of situations where native leaflet bisection may be desirable include situations where native valve leaflets are deforming (or will deform) the prosthetic valve into an undesirable shape (e.g., deforming the prosthetic valve into an oval shape). For example, a heavily calcified native valve leaflet may have portions that combine to distort the prosthetic valve deployed in the annulus.
Another situation where native leaflet bisection may be desirable is for so-called bicuspid aortic valves (BAVs). In BAVs, an aortic valve has only two (2) leaflets (as opposed to the usual three (3) leaflets), or has adjacent leaflets that are fused (e.g., in edge-to-edge alignment along a raphe/fusion between adjacent leaflets) into a single leaflet structure so that the valve only has two (2) or even one (1) effective leaflet. Prior to deployment of a prosthetic valve in such a valve, it may be desirable to bisect a leaflet into two separate leaflet structures, or to separate two fused leaflets (such as by bisecting the fused leaflets along the raphe).
Various devices and methods are known in the art for valve leaflet dissection and removal. For catheter-based valve leaflet dissection, cutting devices are known that can be delivered via a catheter.
In cases where valve leaflet bisection is desirable to facilitate valve repairs and replacements, traditional cutting devices may have difficulty in advancing a cutting element through a leaflet (e.g., due to the tough tissue/deposit materials often associated with damaged valve leaflets, such as calcified valve leaflets).
There is presently a need for an improved means for performing heart valve repairs and replacements. The current invention fulfills this need.